In western nations, the vast majority of sexually active women take the birth control pill at some point in their lives, usually to avoid becoming pregnant. Of increasing interest to some psychologists, the hormone-stabilising effects of the pill may have other important effects, including on the psyche and personal relationships, and these are the focus of a new study in Neurology, Psychiatry and Brain Research.

Some earlier studies found that women who take the pill report more emotional stability, in terms of experiencing fewer depressive symptoms, and fewer mental health problems more generally (of course this is not true of all women, in fact some women describe unwanted emotional effects from the pill). There also appear to be what Tenille Taggart at San Diego State University and her colleagues refer to as “downstream benefits” of taking the pill, including greater relationship stability and satisfaction.

However, before now, no study has measured these two outcomes (emotional stability and relationship satisfaction) simultaneously. Taggart’s team have done this and their results suggest that a key reason that women who take the pill (oral contraceptives; OCs) tend to enjoy more satisfying relationships is because they have more stable emotions.

“Our results support previous findings that OCs may confer positive psychological benefits, and that one of these, mood stability, may have diffuse effects on women’s broader wellbeing and functioning,” they write.

The research involved 282 women (average age 26-27 years) recruited via Amazon’s Mechanical Turk survey website. One hundred and ninety-nine of the women were not taking the oral contraceptive pill, while the remaining 83 were (and had been for an average of 33 months).

The women reported whether they experience mood swings, how often and how severely. They also answered questions about their relationship satisfaction.

Consistent with previous research, on average the women taking the pill reported fewer and less severe mood swings, and they had more satisfying relationships. Statistically speaking, Taggart and her team described the size of these group differences as “notable”.

The novel finding was that the greater emotional stability among the women on the pill mediated the greater relationship satisfaction they reported – that is, statistical analysis suggested that the greater relationship satisfaction in the group on the pill was partly explained by their also tending to have more stable emotions. In fact, 44 per cent of the variance in the women’s relationship satisfaction was accounted for by differences in their emotional stability.

Deeper analysis suggested it was specifically having fewer and less serious up and down mood swings that was related to relationship satisfaction, not having less negative emotion or more positive emotion per se. The researchers speculated that intensity and frequency of negative emotion may be more akin to a personality trait, and that it is specifically emotional lability (mood swings) that is reduced by the birth control pill.

The researchers said their findings “support public policy efforts aimed at providing broad, affordable access to contraceptives, including for non-contraceptive benefits, and discussing OCs as a potential treatment with all women, including those not at imminent risk for pregnancy”.

Others may worry that any potential benefits from this line of research would be outweighed by the stigmatising effect of spreading the idea that women’s emotions (rather than, say, gender inequality) are a problem that needs addressing.

Even for supporters of this research endeavour, more data is clearly needed, especially long-term studies that follow women (and ideally their partners too) over time, so that causal factors can be identified with more confidence. With the current cross-sectional design other interpretations of the results are feasible – for instance, perhaps it is relationship satisfaction that influences women’s choice to take the pill and also reduces their emotional lability.

Did anyone consider the mood stabilising effect that worrying less about unplanned pregnancies could have on women? The pill being a highly effecitve contraception if used correctly does a lot to free women to consider other aspects of their lives including relationship satisfaction.